1. Field of the Invention
The present invention relates to an inspection apparatus for inspecting a fiber having optical connectors, which apparatus measures the return loss and insertion loss of a fiber having optical connectors.
Fibers having optical connectors have been used in considerably broad fields, such as the field of optical transmission systems and the field of optical device measurement. In order to improve production efficiency, a process of manufacturing a fiber having optical connectors is demanded to measure a return loss and an insertion loss, which are basic characteristics of an optical connector, without involvement of intricate operations and within a short period of time.
A related-art method of measuring a return loss of an optical connector will be described by reference to FIG. 5. As shown in FIG. 5, a fiber inspection system 200 having an optical connector for use with the related-art return loss measurement method comprises a light source 1; an optical branch coupler 2; a first optical sensor 3; a refractive index matching material 6; a master optical connector 7; and an optical terminator 20. Optical connectors are provided on both ends of a measured optical fiber 5. In the following description, an optical connector provided on one end of the optical fiber 5 and connected to the master optical connector 7, is called a first optical connector 8, and an optical connector provided on the other end of the optical fiber 5 is called a second optical connector 9.
Conventionally, when the return loss of an optical fiber having connectors is measured, the light source 1 is connected to a first terminal 2a of the optical branch coupler 2, and the first optical sensor 3 is connected to a second terminal 2b of the optical branch coupler 2. The master optical connector 7 is connected to a third terminal 2c of the optical branch coupler 2, and the optical terminator 20 is connected to a fourth terminal 2d of the optical branch coupler 2. Fresnel reflection arising at the master optical connector 7 is received by the first optical sensor 3, and the power of the thus-received light is taken as a reference.
The first optical connector 8 of the measured optical fiber 5 is connected to the master optical connector 7, and the second optical connector 9 of the measured optical fiber 5 is terminated with the refractive index matching material 6. With such an arrangement, light reflected from the measured optical fiber 5 is received by the first optical sensor 3. A difference between the power of the thus-received light and the reference is computed, thereby computing a return loss.
A related-art method of measuring insertion loss of an optical connector will now be described by reference to FIG. 6B. As shown in FIG. 6B, an inspection system 201 for inspecting an optical fiber having connectors and for use with a related-art method of measuring an insertion loss of a connector comprises a light source 1; a master optical connector 7; and an optical sensor 21. A measured fiber 5 is provided with an optical connectors 8 and 9 in the same manner as the measured fiber 5 shown in FIG. 5.
Conventionally, when an insertion loss of an optical fiber having connectors is measured, an output of the light source 1 is connected to an input of the optical fiber, in the same manner as in an inspection system 201xe2x80x2 for inspecting a fiber having optical connectors shown in FIG. 6A. Light output from the master optical connector 7 is received by an optical sensor 21, and the power of the thus-received light Pc is taken as a reference value. In the same manner as in an inspection system 201 for inspecting a fiber having optical connectors shown in FIG. 6B, the measured optical fiber 5 is connected to the master optical connector 7, and light output from the master optical connector 7 is received by an optical sensor 21. A difference between the power Py of the light received by the optical sensor 21 in this case and the reference value Pc is taken as an insertion loss of the connector.
A related-art expression for computing an insertion loss of a connector is expressed as Eq. (1).
IL=xe2x88x9210 log(Pc/Py)+10 log xcex1xe2x80x83xe2x80x83(1) 
where xcex1 represents the transmissivity of an optical fiber.
According to the related-art technique, the return loss of the measured optical fiber 5 and the insertion loss of the same are measured separately through use of different measurement systems. Hence, the measured optical fiber 5 must be reconnected for changing the measurement item. A result of measurement corresponds to measure value of the entire system, including both the measured optical fiber 5 and the optical connectors, thereby rendering vague in a decision as to whether or not processed optical connectors are non-defective.
The present invention is aimed at improving inspection efficiency during a process of manufacturing a fiber having optical connectors, by means of measuring a return loss and an insertion loss, which are basic characteristics of an optical connector, without reconnection of an optical fiber to be measured.
In order to solve the drawbacks, a first aspect of the present invention provides an inspection apparatus for inspecting an optical fiber having two optical connectors at both ends thereof, comprising:
an optical branch coupler (for example, an optical branch coupler 2 shown in FIG. 1) having a first to four input/output terminal (for example, a first terminal 2a, a second terminal 2b, a third terminal 2c, and a fourth terminal 2d, which are shown in FIG. 1), the optical branch coupler branching and outputting light to third and fourth terminals when the first or second terminal is taken as an input terminal, the optical branch coupler branching and outputting light to the first and second terminals when the third or fourth terminal is taken as an input terminal;
a light source (for example, a light source 1 shown in FIG. 1) connected to the first terminal of the optical branch coupler;
a first optical sensor (for example, a first optical sensor 3 shown in FIG. 1) connected to the second terminal of the optical branch coupler;
a second optical sensor (for example, a second optical sensor 4 shown in FIG. 1) connected to the fourth terminal of the optical branch coupler;
a master optical connector (for example, a master optical connector 7 shown in FIG. 1) connected to the third terminal of the optical branch coupler; and
a measurement unit (for example, a measurement unit 10 shown in FIG. 2),
wherein Fresnel reflection occurs in a state where the master optical connector is released, power of the Fresnel reflection received by the first optical sensor is defined as a first reference;
the measurement unit measures an insertion loss based on the first reference and power of light received by the first optical sensor when one of two optical couplers of the optical fiber is connected to the master optical connector and the other thereof is released; and
when one of two optical couplers of the optical fiber is connected to the master optical connector and the other thereof is terminated, the measurement unit measures a return loss based on power of light received by the first optical sensor and power of light emitted from the light source and received by the second optical sensor.
According to a first aspect of the present invention, the light source is connected to the first terminal of the optical branch coupler having four input/output terminals; the first optical sensor is connected to the second terminal of the same; the master optical connector is connected to the third terminal of the same; and the second optical connector is connected to the fourth terminal of the same. Fresnel reflection occurs in a state where the master optical connector is released, and power of the Fresnel reflection received by the first optical sensor is defined as a first reference. The measurement unit measures an insertion loss based on the first reference and power of light received by the first optical sensor when one of two optical couplers of the optical fiber is connected to the master optical connector and the other thereof is released. When one of two optical couplers of the optical fiber is connected to the master optical connector and the other thereof is terminated, the measurement unit measures a return loss based on power of light received by the first optical sensor and power of light emitted from the light source and received by the second optical sensor.
Accordingly, the return loss and insertion loss of the optical fiber can be measured through use of the single measurement system, thereby obviating a necessity for reconnecting the optical fiber according to measurement items. Eventually, production efficiency in a process of manufacturing a fiber having optical connectors is improved.
In a second aspect of the present invention, the inspection apparatus according to the first aspect, further comprises:
a unit transmission loss storage section (for example, RAM 14 shown in FIG. 2) adapted to store a transmission loss of the optical fiber per unit-length in advance; and
an input unit (for example, an input unit 12 shown in FIG. 2) adapted to input a length of the optical fiber,
wherein the measurement unit includes a connector insertion loss computation section (for example, a CPU 11 shown in FIG. 2) adapted to compute a transmission loss of the optical fiber from the transmission loss of the optical fiber per unit-length and the length of the optical fiber, the connector insertion loss computation section adapted to compute an insertion loss of an optical connector portion by means of subtracting the transmission loss of the optical fiber from the insertion loss.
According to the second aspect of the invention, the transmission loss of the optical fiber per unit length is stored in the unit transmission loss storage section in advance, and the input unit inputs the length of the optical fiber. The connector insertion loss computation section of the measurement unit computes the transmission loss of the optical fiber from the transmission loss of the optical fiber per unit-length stored in the unit transmission loss storage unit and the length of the optical fiber input by the input unit. Further, the connector insertion loss computation unit computes the insertion loss of the optical connector by means of subtracting the computed transmission loss of the optical fiber from the insertion loss.
In third aspect of the invention, the inspection apparatus according to the first aspect, further comprising a fiber transmission loss storage section (for example, RAM 14 shown in FIG. 2) adapted to store in advance a transmission loss of the optical fiber, and
the measurement unit includes a connector insertion loss computation section (for example, a CPU 11 shown in FIG. 2) adapted to compute an insertion loss of a optical connector portion by means of subtracting the transmission loss of the optical fiber from the insertion loss.
According to the third aspect of the invention, the transmission loss of the optical fiber is stored in the fiber transmission loss storage unit in advance. The connector insertion loss computation section of the measurement unit computes the insertion loss of the connector portion by means of subtracting the transmission loss of the optical fiber stored in the fiber transmission loss storage unit from the insertion loss.
According to the second and third aspect of the invention, the transmission loss of the optical fiber can be subtracted from a measurement result of the insertion loss. Hence, the insertion loss of the optical connector portion becomes definite, thereby enabling easy determination as to whether or not a processed optical connector is non-defective.
In fourth aspect of the invention, the inspection apparatus according to the first aspect, further comprises:
a unit backscattering amount storage section (for example, RAM 14 shown in FIG. 2) adapted to store an amount of backscattering of the optical fiber per unit-length in advance; and
an input unit (for example, an input unit 12 shown in FIG. 2) adapted to input a length of the optical fiber,
wherein the measurement unit includes a connector return loss computation section (for example, a CPU 11 shown in FIG. 2) adapted to compute an amount of backscattering of the optical fiber from the amount of the backscattering of the optical fiber per unit-length and the length of the optical fiber, the connector return loss computation section adapted to compute a return loss of an optical connector portion by means of subtracting the amount of the backscattering of the optical fiber from the total return loss.
According to the fourth aspect of the present invention, the amount of the backscattering of an optical fiber per unit-length is stored in the unit backscattering storage unit in advance, and the length of the optical fiber is input by input unit. The connector return loss computation section of the measurement unit computes the amount of the backscattering of the optical fiber from the amount of the backscattering of the optical fiber per unit-length stored in the unit backscattering storage unit and the length of the optical fiber input by the input unit. The connector return loss computation unit computes the return loss of the optical connector by means of subtracting the amount of the backscattering of the optical fiber from the return loss.
In fifth aspsect of the invention, the inspection apparatus according to the first aspect, further comprises an optical fiber backscattering amount storage section (for example, RAM 14 shown in FIG. 2) adapted to store an amount of backscattering of the optical fiber beforehand, wherein the measurement unit includes a connector return loss computation section (for example, a CPU 11 shown in FIG. 2) adapted to compute a return loss of an optical connector portion by means of subtracting the amount of the backscattering of the optical fiber from the total return loss.
According to the fifth aspect of the invention, the amount of the backscattering of the optical fiber is stored in optical fiber backscattering storage unit in advance. The connector return loss computation section of the measurement unit computes the return loss of the optical connector portion, by means of subtracting the amount of the backscattering of the optical fiber stored in the optical fiber backscattering storage section from the return loss.
Hence, according to the fourth and fifth aspect of the present invention, the amount of the backscattering of the optical fiber can be subtracted from the measurement result of the return loss. Accordingly, the insertion loss of the optical connector becomes definite, thereby enabling an easy determination as to whether or not a processed optical connector is non-defective. Particularly, the present invention is effective in the case of a long optical fiber.
In sixth aspect of the invention, the inspection apparatus according to the first to fifth aspect, further comprises
a defective/non-defective determination reference value setting unit (for example, an input unit 12 and RAM 14, which are shown in FIG. 2) adapted to set defective/non-defective determination reference values in relation to a return loss and an insertion loss, respectively; and
a determination section (for example, a CPU 11 shown in FIG. 2) adapted to determine whether or not the optical fiber having the optical connectors is defective, by means of comparing the defective/non-defective determination reference values with the total return loss and the total insertion loss, respectively.
According to the sixth aspect of the invention, the defective/non-defective determination reference value setting unit sets the defective/non-defective determination reference value in relation to the return loss and the insertion loss. The determination section determines whether or not the optical fiber having the optical connectors is defective, by means of comparing the defective/non-defective determination reference values with the return loss and the insertion loss measured by the measurement unit, respectively.
Since the determination as to whether or not the optical fiber having the optical connectors is non-defective is made automatically, whether or not the optical fiber is non-defective can be readily checked, without involvement of an examination of real data concerning the return loss and the insertion loss. Thus, the optical fiber having the optical connectors can be inspected efficiently.